For evaluating the significance of intraoperative electrophysiologic monitoring and observing the change of clinical and electrophysiologic results after Microvascular Decompression(MVD), we did follow-up 227 cases with hemifacial spasm, who had been operated at Bong Seng Memorial Hospital and Dong Rae Bong Seng Hospital, for more than 2 months. For comparing, we divided patients into Monitoring group(n=134) and Non-monitoring group(n=93). The success rate of MVD was 89.5% at POD 7 and 92.3% at follow-up, respectvely, and there was no statistical difference between Monitoring and Nonmonitoring group. But the distribution of offenders was only statistically different from each other. During follow-up, the clinical results changed at 59 cases of 142(41.5%), and hemifacial spasm in 32 cases gradually disappeared. In the 57 cases, which were able to test follow-up electrophysiologic study, 73.7% electrophysiologically changed, and the ratio of completely disappeared Abnormal Muscle Response was statistically increased from 35.1% at POD 7 to 70.2% at follow-up study. In the 85 cases, which were able to followup at Monitoring group, the results of electrophysiologic study at POD 7 were statistically correlated with clinical results at follow-up.

According to the above results, electrophysiologic study is helpful for identifying the offenders and determining the adequacy of vascular decompression, clinical and electrophysiologic status of hemifacial spasm after MVD has continuously changed, and the results of electrophysiologic study at POD 7 are useful for predicting the clinical results at follow-up.